The primary function of the human esophagus is the transport of solid and liquid nourishment from the mouth to the stomach. The esophagus has inherent coordinated contractile capabilities, providing peristalsis of material in an antegrade direction (towards the stomach). Further, the esophagus secretes a neutral pH mucous to lubricate the passage of food, as well as to protect its lining from acid induced injury. The stomach contains a mixture of food and liquid from oral intake, acid and enzymes from the stomach lining, and bile and enzymes from the liver and pancreas. The lower esophageal sphincter and diaphragmatic muscles act as a valve at the junction of esophagus and stomach, preventing reflux of stomach contents into the esophagus. This lower esophageal sphincter normally remains closed until parasympathetic activation or approach of a food bolus causes its relaxation, allowing food to pass into the stomach from the esophagus. Distension of the stomach, particularly the cardiac portion of the stomach, causes an abrupt relaxation of the lower esophageal sphincter resulting in a venting event (belch). Certain foods, medication, and beverages containing caffeine or theophylline (xanthines) may predispose the lower esophageal sphincter to inappropriate relaxations, and subsequent reflux. Anatomical effects related to aging or hiatal hernia may also predispose a patient to reflux.
Patients having abnormal function of the lower esophageal sphincter may present with symptoms of dysphagia (difficulty in swallowing), heartburn due to reflux, chest pain, and other related symptoms. A common sign of chronic gastroesophageal reflux is erosive esophagitis.
When chronically exposed to injurious stomach contents, the esophageal lining may breakdown leading to inflammation, erosion or ulceration. Chronic GERD and the resultant erosive esophagitis can lead to a pre-cancerous condition, known as Barrett's esophagus or intestinal metaplasia, which is injury-related genetic change in the epithelial cells.
As described for example in copending, commonly owned U.S. application Ser. No. 10/754,445, filed Jan. 9, 2004, a treatment catheter having an expandable electrode support can be used for treating a circumferential region of the esophagus in order to ablate an abnormal mucosal layer of the esophagus using radiofrequency (RF) energy. When successful, the treatment results in regeneration of a normal mucosal layer substantially free from metaplastic and other damaged epithelial cells characteristic of Barrett's esophagus.
In some instances, however, such radiofrequency ablation treatment may not be entirely successful and one or more regions of abnormal mucosa may remain. These focal areas may be approached with a device designed with a surface area more suited to ablating focal areas of mucosal disease. Further, some patients with Barrett's esophagus may present at baseline with very limited disease, either non-circumferential or very short segments that also would be better suited for focal ablation rather than circumferential ablation.